Conceptual Modelling of Pit Lake Processes and Ecological Risk

Clint McCullough (MiWER), Mark Lund (MiWER)

Conceptual modelling to better understand ecological risks posed by pit lakes

To ensure greatest scientific robustness of conceptual models we held a site visit and workshop in Collie with an expert panel of scientific researchers and managers from universities and State regulatory staff to best understand how these processes are likely working in different pit lakes. This workshop identified conceptual model needs e.g., a carbon cycling model and an acidity budget model. The intent is to then present the conceptual models as diagrammatic representations highlighting the nature of relationships between parameters and processes. These models will also be used to develop cohorts of similar pit lakes for later empirical modelling.


Photo: How does acidity enter Collie pit lakes? (Lake Kepwari)


Figure: Example conceptual modelling of pit lake chemistry

Funding: Department of Water (Western Australia)

Outputs

McCullough, C. D. & Lund, M. A. (2010). Mine Voids Management Strategy (IV): Conceptual Models of Collie Basin Pit Lakes. Department of Water Project Report MiWER/Centre for Ecosystem Management Report 2010-12, Edith Cowan University, Perth, Australia. 95pp. Unpublished report to Department of Water. link

McCullough, C. D. & Van Etten, E. J. B. (2011). Ecological engineering of a novel lake district: new approaches for new landscapes. Mine Water and the Environment. 30: 313-319.link

Assessment of the Effects of Pit Lakes on Human Health

Andrea Hinwood (CEM), Jane Heyworth (UWA), Helen Tanner (CEM), Clint McCullough (MiWER)

Do pit lakes present a hazard to human health?

Government and community stakeholders have expressed concerns about how open cut mining operations may affect human health and wellbeing through modified surface and groundwater regimes and their follow-on effects on environmental contamination and disease propagation. This project used Collie as a case-study to investigate how the formation of pit lakes may degrade or even improve health outcomes for mining communities living with these legacies.

This project aimed to examine possible impacts of human interaction with pit lakes. The project was conducted in three stages. The first was a literature review of the health effects of the aspects of pit lakes including chemical contamination, pH and also injury. The second stage of the work attained an understanding of how and how frequently the community was exposed to the pit lakes leading to the third stage, an assessment of the risks of exposure and health impacts. Stage 3 produced a screening health risk assessment identifying risks, management strategies, including management trigger levels to ensure protection of human health.

 


Photo: Sulfidic minerals release acidity and metals as AMD in Collie pit lakes


Photo: Black Diamond pit lake highwalls create a realised drowning risk

Stage 1:  Literature review of historic and new Collie pit lake characteristics, data collation of existing information and assessment of health impacts of identified parameters.

This stage required the compilation of existing data on the chemical, physical and biological aspects of Collie pit lakes from the peer reviewed and available grey literature. As there was little data publicly available on Collie pit lakes, this data compilation made extensive use of unpublished MiWER data. Project members from the MiWER team have an extensive dataset on water quality of most Collie pit lakes extending back more than a decade and also collected new data specifically for the health study. In addition, existing monitoring data was used to determine concentrations of relevant parameters and their likely health effects. The literature review outlined likely health effects associated with water temperature and other issues such as chemical injury. The data collated in Task 1 were used to identify potential chemical and biological human health risks associated with pit lakes in Collie. A further literature review also examined physical risks such as injury, water temperature and drowning.  

Stage 2:  Community Survey

To assess the use and perceived issues of using pit lakes a community survey was undertaken via administration of a postal questionnaire. The questionnaire was focussed on finding out how many people use the pit lakes, the purposes for which they use the lake, how often they use the lakes and for how long they have used the lakes and how they would like to use the lakes. We also obtained data on health issues that may be associated with pit lake water and other potential confounding factors. The questionnaire was designed based on the literature review. The population of Collie and surrounds is 7,194 persons and we aimed to obtain information from approximately 10% of the population. As response fractions are often low 1,500 questionnaires were posted to a random sample of residents of Collie. The selection was based on the electoral roll. A reply paid envelope was provided. The data collected via questionnaire was analysed and the information informed the screening health risk assessment in Stage 3. A report on the questionnaire was then developed and provided the Department with a variety of information on actual and perceived issues associated with pit lakes in the area. 

Stage 3:  Screening Health Risk Assessment.

Health risk assessment is a systematic, transparent process of assessing the potential risks associated with exposure to environmental and physical parameters. It uses a standard methodology which is routinely accepted worldwide and provides managers with good information on how to prevent and minimise both actual and perceived risks. Based on Stages 1 and 2 human health risks were determined based on the likelihood of them occurring, the consequence if they occur and therefore an assessment of the significance of the risk. This process also enabled the development of triggers to manage issues to prevent risks from occurring. This stage also identified any issues that required further investigation.

Funding: Department of Water (Western Australia)

Outputs

Hinwood, A.; Tanner, H.; Heyworth, J.H.; McCullough, C. D. & Lund, M. (2010). Water quality of mine void pit lakes used for recreation. 2010 Joint Conference of International Society of Exposure Science & International Society for Environmental Epidemiology. Seoul, Korea. International Society of Exposure Science (ISES) and the International Society of Environmental Epidemiology (ISEE).PDF

Hinwood, A.; Tanner, H.; Heyworth, J. & McCullough, C. D. (2010). Recreational use of acid mine pit lakes. 2010 Joint Conference of International Society of Exposure Science & International Society for Environmental Epidemiology. Seoul, Korea. International Society of Exposure Science (ISES) and the International Society of Environmental Epidemiology (ISEE). PDF

Hinwood,A.; Heyworth, J.; Tanner, H. & McCullough, C. D. (2012). Recreational use of acidic pit lakes – human health considerations for post closure planning. Journal of Water Resource and Protection. 4: 1,061-1,070 link

Hinwood, A. L.; Heyworth, J.; Tanner, H. & McCullough, C. D. (2010). Mine Voids Management Strategy (II): Review of potential health risks associated with Collie pit lakes. Department of Water Project Report MiWER/Centre for Ecosystem Management Report 2010-11, Edith Cowan University, Perth, Australia. 111pp. Unpublished report to Department of Water. link